Abstracts and Available Papers Presented at the
1997 International RERTR Meeting

EVALUATION OF REACTOR KINETIC PARAMETERS
WITHOUT THE NEED FOR PERTURBATION CODES

M. M. Bretscher

Argonne National Laboratory
Argonne, Illinois 60439-4841 USA

ABSTRACT

The analysis of research reactor transients depends on the effective delayed neutron fraction (b_eff), its family-dependent components (b_eff,i), the prompt neutron lifetime (l_p), and the decay constants (l_i) for each delayed neutron family. Beginning with ENDF/B-V data, methods are presented for accurately calculating these kinetic parameters within the framework of diffusion theory but without the need for a perturbation code. For heavy water systems these methods can be extended to include the delayed photoneutron component of b_eff. However, a separate calculation is needed to estimate the fractional loss of fission product gamma rays, energetic enough to dissociate the deuteron, from leakage, energy degradation and absorption in fuel and structural materials. These methods are illustrated for a light-water Oak Ridge Research Reactor (ORR) LEU core and for a heavy-water Georgia Tech Research Reactor (GTRR) HEU core where calculated and measured values of the prompt neutron decay constant (b_eff/l_p) are compared.